The invention relates to a supporting roller set for tiltable, axially movable and rotatable support for a rotary drum which can be driven in rotation, such as a rotary kiln, rotary dryer and the like, according to the preamble to claim 1.
In order that rotary drums with relatively large dimensions, not only with regard to the diameter but also with regard to the length, can be reliably supported or mounted, use is madexe2x80x94as is generally knownxe2x80x94of at least two supporting roller sets which are disposed at a corresponding axial distance from one another. In the case of such rotary drums with large dimensions, such as for example rotary kilns, rotary dryers and the like, it is not possible to avoid the occurrence, on the one hand, of certain inaccuracies of assembly and, on the other hand, of more or less great deformations and distortions of the appertaining drum shell, which manifest themselves particularly severely in the case of rotary drums with a strong heat effect, as in the case of rotary kilns. In practical operation this leads to wobbling movements in the region of the running surfaces which support such a rotary drum on the corresponding supporting rollers and are formed by riding rings mounted on the corresponding sections of the drum. In order to be able to compensate for impaired supporting action due to such wobbling movements of the rotary drum running surfaces and to reduce the resulting abrasion (wear) and damage to the circumferential surfaces or running surfaces which are in engagement with one another, numerous embodiments of supporting roller sets are already known in which the supporting rollers and/or the bedplates bearing them are supported so as to be tiltable or axially movable relative to a stationary
In this case it should basically be noted that the irregular supporting action in the contact surface between two touching cylinders, which has already been addressed above, can be caused by a so-called xe2x80x9cskewingxe2x80x9d and/or by a so-called xe2x80x9cedge supportxe2x80x9d. xe2x80x9cSkewingxe2x80x9d is understood to mean the situation where the parallel central axes of two touching cylinders are twisted relative to one another about their common connecting normal, so that the twisted central axis have no common point of intersection. In such skewing an irregular pressure distribution occurs in the contact surfaces with the maximum in the middle of the contact surfaces (viewed over the length of the cylinder), and additionally in the rolling operation between the circumferential surfaces of the cylinders (e.g. between the riding ring of a rotary drum and a supporting roller) the skewing produces axial forces, i.e. forces in the direction of the cylinder axes, in the contact surfaces when corresponding opposing forces (e.g. a so-called xe2x80x9cslope take-off forcexe2x80x9d of a rotary kiln which acts axially) are present. xe2x80x9cEdge supportxe2x80x9d is understood to mean the situation where the parallel central axes of two touching cylinders are twisted relative to one another in their common plane, so that the twisted central axes have a common point of intersections. In this edge support the so-called xe2x80x9cHertzian pressurexe2x80x9d is distributed irregularly over the contact surfaces on the length of the cylinders, i.e. the resulting pressure from the integration of the surface pressure (Hertzian pressure) acts unilaterally radially on the touching cylinders.
In practice attempts are made to prevent the skewing and edge support by the use of self-adjusting supporting rollers or supporting roller systems and thus to achieve a favourable contact pattern (constant Hertzian pressure) between the rotary drum running surfaces and the outer circumferential surfaces of the supporting rollers as far as possible in all operating conditions. In order to be able to follow all possible movements (wobbling etc.) of the running surfaces, the bedplate of a supporting roller would for example have to be mounted so that it has at least two degrees of freedom in rotation about the theoretical axes of the skewing and of the edge support. A spherical bearing would of course meet this requirement. However, in such a bearing an unstable mechanical system is produced, i.e. the supporting roller can move in an uncontrolled manner relative to the rotary drum running surface. The critical degree of freedom of this self-adjustment is the rotation about the theoretical axis of rotation of the skewing, the skewing of the supporting roller being caused by eccentric circumferential forces (tractive forces in the case of non-driven supporting rollers and driving forces in the case of driven supporting rollers). As the rotation or skewing increases no restoring forces are produced on the supporting roller, so that the supporting roller goes out of control. Such a system is not capable of functioning.
In order to avoid the described instability, it is known in the art to mount the bedplate of a self-adjusting supporting roller so that no uncontrollable skewing can occur, i.e. of the two necessary degrees of freedom of the self-adjusting bearing of the bedplate the degree of freedom of the skewing is dispensed with. The remaining degree of freedom prevents the edge support between the rotary drum running surface and the supporting roller. The bedplate thus mounted with the firmly connected supporting roller follows the rotary drum running surface (riding ring) through tilting movements only in one direction and thus prevents the said edge support. The position of the theoretical axis of rotation about which the tilting movements take place plays a significant role in the susceptibility of the self-adjustment to axial forces on the part of the rotary drums.
In a construction which is known from EP-A-0 109 136 and corresponds approximately to the supporting roller set, the supporting roller is supported on its axle via two rotary bearings by the two ends of a tiltable bedplate. This bedplate is mounted by means of a central self-orienting roller bearing essentially in the form of a circular cylindrical part which is in movable contact with the inner face of a bearing shell in the form of an annular cylinder segment, the outer face of which is supported on a horizontal foundation plate. The self-orienting bearing in the form of a circular cylindrical part and the bearing shell or the cylinder segment form as an entity the actual self-orienting bearing for the bedplate. Since the inner face of the cylinder segment is equipped with a sliding surface the self-orienting bearing supporting the bedplate can move along the inner sliding surface of the cylinder segment, and during this movement the cylinder segment carries out a pendulum movement on the foundation. In order that the bedplate and the supporting roller borne by it can carry out an axial displacement corresponding to the axial movement of the rotary drum riding ring, mechanical or hydraulic drive means are provided which can be correspondingly actuated by the riding ring. The two supporting rollers of a supporting roller set can be borne by a common bedplate, a separate self-orienting bearing being disposed below each roller; however, it is also possible to support each of the supporting rollers on a separate bedplate and then to connect the two bedplates to one another by way of clamping cables or clamping rods to absorb expansion forces.
If in the known construction last described (EP-A-0 019 136) the skewing explained above is to be adjusted, then this is obviously only possible by a displacement on the bedplate of the rotary bearing supporting the supporting roller axle. Such a displacement of the rotary bearing of the supporting roller axle on the bedplate requires relatively high construction costs and is only possible with special heavy tools and with a relatively high consumption of time. If in this known construction two separate bedplates are provided for the two supporting rollers, then the clamping rods or the like must be constructed so as to absorb relatively high expansion forces and torsional forces.
The object of the invention is to create a supporting roller set which avoids edge support and at least largely avoids skewing and which with relatively simple design and reliable operation ensures an optimal self-adjustment with easy action of each supporting roller.
This object is achieved according to the invention by the features set out.
Advantageous embodiments and variants of the invention are the subject matter of the subordinate claims.
The invention is based upon the knowledge that a self-adjusting supporting roller of a supporting roller set must, in addition to having a stable running, fulfil at least the following requirements:
a) The mounting of the tiltable bedplate must have an easy action so that the supporting roller can follow the wobbling deflections of the running surface or of the riding ring of the rotary drum to be supported without high adjusting moments, any remaining edge support being determined by necessary adjusting moments of the bedplate mounting
b) Each self-adjusting supporting roller should not react to forces in the direction of the supporting roller axis (axial forces), i.e. the axial forces which are always present should not influence the supporting action.
c) Unavoidable self-oscillations (every component has self-oscillations) of the self-adjusting supporting rollers should remain unaffected by forces (or their changes over time) in the contact surface between the rotary drum running surface and the supporting roller, because incitation of self-oscillations by these forces would lead to irregular wear on the outer circumferential surface of the supporting rollers.
Therefore in the supporting roller set according to the invention each bedplate bearing a supporting rollerxe2x80x94when viewed transversely with respect to the rotary drum and to the supporting rollersxe2x80x94is supported on the foundation by way of two articulated bearings which are transversely spaced from one another, of which the inner articulated bearing which lies nearer to the vertical longitudinal central axis of the rotary drum is constructed in the form of a ball-and-socket bearing and as a fixed bearing is disposed statically on the foundation, whilst the outer articulated bearing which lies further away from this vertical longitudinal central plane forms a movable bearing and is supported so as to be slidably movable on the foundation approximately in the shape of an arc of a circle about the central point of the ball of the inner ball-and-socket bearing.
This construction according to the invention facilitates optimal easy-action self-adjustment of each bedplate and thus of the supporting roller borne by this bedplate, wherein the supporting rollers and the bedplates bearing them are stabilised by the running surfaces or riding rings of the rotary drum which are supported on the outer circumferential surfaces, but in this case due to their easy-action tiltability (by way of the articulated bearing) and by way of the approximately arcuate slidably movable support on the foundation they create the precondition so that on the one hand an unwanted edge support is avoided and on the other hand any unwanted skewing of each supporting roller can be stopped quickly and with little work involved by a corresponding sliding movement of the outer articulated bearing on the foundation.
In this case it is particularly advantageous if an adjusting device is provided in the region of the outer articulated bearing and acts on the bedplate in such a way that this bedplate is displaceable in the direction of the arcuate slidably movable support of the outer articulated bearing relative to the foundation and thus the supporting roller borne by it is adjustable or readjustable in the sense of a skewing adjustment relative to the rotary drum running surface.
It is also regarded as advantageous if the two articulated bearings of the or of each bedplate are essentially constructed as axial articulated bearings and if in the normal position of supporting roller and bedplate the central axis of the inner articulated bearing is oriented so that it is inclined with respect to the horizontal, this inclination being determined by the direction of action of the resultant forces acting on the appertaining supporting roller, i.e. this inclination or angled position of the inner ball-and-socket bearing results from the vectorial addition of circumferential forces (e.g. bearing frictional forces and driving forces) and bearing forces on the or each supporting roller.
A mere comparison of this previously described construction according to the invention with last-described known construction (EP-A-0 019 136) makes clear on the one hand the extremely simple and quick possibility for adjustment in the case of skewing of the or each supporting roller, i.e. skewing caused for example by axial forces on the part of the rotary drum can be eliminated in an extremely simple manner and with little consumption of time and energy. On the other handxe2x80x94in contrast to the said known constructionxe2x80x94due to the design according to the invention expansion forces are absorbed by the inner ball-and-socket bearing which is constructed as a fixed bearing, so that no special elements are necessary for absorption of torsional forces.
In so afar as the adjusting device for adjustment of the skewing of the supporting roller is concerned, this can be constructed in a particularly advantageous and simple manner in that it comprises two adjusting screws which lie axially spaced opposite one another, are movable relative to one another and act substantially horizontally, as well as a stop element, the lateral faces of which form stop or contact surfaces for the ends of these screws. Thus the skewing adjustment or the adjustment of each bedplate and of the supporting roller borne by it relative to the rotary drum running surface can be carried out in an extremely simple manner using a very simple hand tool, for example a spanner, and also quickly and with little force.